Construction machine

ABSTRACT

A construction machine includes an exhaust duct for discharging a lower airflow to the exterior of an engine room. An air inlet for introducing air into the exhaust duct is provided in an upper portion of the exhaust duct, and an air outlet for discharging the air from the exhaust duct is provided in a lower portion of the exhaust duct. An air passage is formed in the interior of the exhaust duct between the air inlet and the air outlet. The exhaust duct is disposed on an exhaust side of the engine room such that the air introduced into the air passage in the exhaust duct through the air inlet is discharged below the engine room from the air outlet through a discharge port, and such that a hydraulic pump provided on the exhaust side of the engine room is shielded from the discharge port by the exhaust duct.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a construction machine such as adigger, in which an exhaust structure is provided to discharge a lowerairflow that flows under an engine in an engine room.

2. Background Art

The background art will now be described, using a digger as an exampleof a construction machine.

As shown in FIG. 8, a digger includes a lower propelling body 1, anupper slewing body 2 that is carried on the lower propelling body 1 tobe free to slew, various pieces of equipment and various devices carriedon an upper frame 3 serving as a base of the upper slewing body 2, and awork attachment (also referred to as a digging attachment) 5 attached toa front portion of the upper frame 3. The various pieces of equipmentcarried on the upper frame 3 include a cabin 4. In FIG. 8, CW denotes acounterweight attached to a rear end portion of the upper frame 3.

Note that in this specification, a position of the cabin 4 is set as aleft side front portion, and “front-rear” and “left-right” directionsare based on the position of the cabin 4.

Further, to simplify the drawings and the description, detailedillustration and description of respective portions of the upper frame,which are not directly related to the present invention, have beenomitted.

An engine room 7 housing an engine 6 is provided in a rear portion ofthe upper frame 3.

FIG. 9 is a schematic sectional view showing an arrangement of devicesin the engine room 7 from a back surface side.

As shown in FIG. 9, the engine room 7 is a space that is long in theleft-right direction and surrounded by a base plate 8 of the upper frame3, an engine guard member 9 such as a panel material, the counterweightCW shown in FIG. 8, and so on. A bottom surface of the engine room 7 isformed by the base plate 8 of the upper frame 3. The engine 6 isdisposed in the engine room 7 via a mounting member, not shown in thedrawing, so as to extend in the left-right direction.

Meanwhile, a left-right pair of vertical plates 10, 11 doubling asreinforcing members and attachment mounting members are provided in anintermediate portion, in a vehicle width direction, of the base plate 8of the upper frame 3. The vertical plates 10, 11 are provided at aninterval in the left-right direction so as to extend perpendicularly tothe base plate 8 along substantially an entire length of the base plate8 in the front-rear direction. The engine 6 is disposed above thevertical plates 10, 11.

As a result, a ventilation gap S through which air can pass is formed inthe engine room 7 below the engine 6.

Further, a fan 12 and a heat exchanger 13 such as a radiator or an oilcooler are provided on one side of the engine 6, or more specifically aright side of the engine 6, while a hydraulic pump 14 is provided on anopposite side of the engine 6, or more specifically a left side of theengine 6. An intake port 15 is provided in the vicinity of a right endof an upper surface wall covering an upper surface of the engine room 7.When the fan 12 is rotated, outside air is taken into the engine room 7through the intake port 15, and the intake air forms a cooling airflowthat flows through the engine room 7 from the right side to the leftside. The heat exchanger 13 and the engine 6 are cooled by this airflow.

Japanese Patent Application Publication No. 2005-186910 discloses aconventional technique for improving a discharge performance of a lowerairflow, which forms a part of the aforesaid airflow that passes throughthe ventilation gap S, as shown by an arrow in FIG. 9. This conventionaltechnique will now be described on the basis of FIG. 9.

In this conventional technique, a fire wall 17 is provided on the leftside, or in other words the hydraulic pump 14 side, of the engine room7. The fire wall 17 is provided to partition the engine 6 from thehydraulic pump 14. The fire wall 17 is provided to prevent mist-form oilthat is leaked or scattered from the hydraulic pump 14 from falling ontothe engine 6, or more accurately an exhaust system of the engine 6including a muffler 16.

Further, an air passage forming member 18 is attached between a lowerend of the fire wall 17 and the base plate 8 of the upper frame 3. Theair passage forming member 18 is formed in an inverted L shape such thatan upper portion thereof is disposed horizontally and a lower portion isdisposed vertically. An air passage 19 that communicates with theventilation gap S is formed by the air passage forming member 18, theleft vertical plate 10, and the base plate 8 of the upper frame 3.Further, an exhaust chamber 20 is defined in a left side region of theengine room 7 by the air passage forming member 18 and the fire wall 17.

Furthermore, an air passage outlet 21 is formed to open in a verticalpart of the air passage forming member 18. A lower portion exhaust port22 is opened in a part of the base plate 8 of the upper frame 3 thatforms a lower surface of the exhaust chamber 20. An upper portionexhaust port 23 is provided in a part of an upper surface wall of theengine guard member 9 that forms an upper surface of the exhaust chamber20. The lower airflow passing through the ventilation gap S enters theexhaust chamber 20 through the air passage 19 and the air passage outlet21, and is discharged to the outside through the two exhaust ports 22,23.

With the configuration described above, the lower airflow is caused toflow smoothly on the exhaust side, thereby improving an air dischargeperformance.

Incidentally, in the conventional technique described above, thehydraulic pump 14 penetrates the fire wall 17 so as to infiltrate theexhaust chamber 20. Therefore, the hydraulic pump 14 can be seen clearlyfrom the exterior of the exhaust chamber 20 through the two exhaustports 22, 23, and as a result, pump noise cannot be blocked completelyfrom the outside. Hence, an increase in pump noise leakage to theoutside, including “direct sound” emitted directly to the exterior ofthe exhaust chamber 20 from the hydraulic pump 14, occurs.

Furthermore, in the conventional technique described above, when anattempt is made to reduce pump noise leakage using a sound absorbingmaterial such as glass wool, a sufficient sound absorption effect cannotbe obtained unless the sound absorbing material is provided over a widerange of the exhaust chamber 20, including the vicinity of the exhaustports 22, 23.

Therefore, an amount of used sound absorbing material increases, leadingto an increase in cost, and moreover, when the sound absorbing materialis provided over a wide range of the exhaust side, devices disposed onthe exhaust side, not shown in the drawings, cannot easily be installeddue to limitations on sizes and positions of the devices.

SUMMARY OF THE INVENTION

An object of the present invention is to suppress pump noise leakagefrom a construction machine while improving an air discharge performanceof a lower airflow that flows under an engine, and when a soundabsorbing material is provided, to facilitate device installation whilesecuring a superior sound absorption effect with a small amount of thesound absorbing material.

A construction machine according to an aspect of the present inventionincludes: an engine room; a floor constituting a bottom surface of theengine room; an engine provided in the engine room such that aventilation gap is formed below the engine; a hydraulic pump provided inthe engine room on an exhaust side serving as one side of the engine; afan which is provided in the engine room on an intake side serving as anopposite side of the engine to the hydraulic pump, and which, when thefan is rotated, generates a cooling airflow that includes a lowerairflow passing through the ventilation gap and flows from the intakeside to the exhaust side; and an exhaust duct formed of a hollow body todischarge the lower airflow to an exterior of the engine room, wherein adischarge port is provided in a part of the floor on the exhaust side,an air inlet for introducing air into the exhaust duct is provided in anupper portion of the exhaust duct, an air outlet for discharging the airfrom the exhaust duct is provided in a lower portion of the exhaustduct, an air passage is formed in an interior of the exhaust ductbetween the air inlet and the air outlet, and the exhaust duct isdisposed on the exhaust side of the engine room such that the airintroduced into the air passage in the exhaust duct through the airinlet is discharged below the engine room from the air outlet throughthe discharge port and the hydraulic pump is shielded from the dischargeport by the exhaust duct.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view showing an upper frame includingan exhaust duct, which is provided in a construction machine accordingto a first embodiment of the present invention;

FIG. 2 is a schematic plan view showing a rear portion of the upperframe shown in FIG. 1;

FIG. 3 is a schematic side view showing the upper frame shown in FIG. 1;

FIG. 4 is a schematic sectional view showing an engine room of theconstruction machine according to the first embodiment of the presentinvention and devices disposed therein;

FIG. 5 is a perspective view showing the exhaust duct;

FIG. 6 is a view corresponding to FIG. 2 and showing an upper frameaccording to a second embodiment of the present invention;

FIG. 7 is a view corresponding to FIG. 4 and showing an engine room of aconstruction machine according to a third embodiment of the presentinvention and devices disposed therein;

FIG. 8 is a schematic side view showing a digger serving as an exampleof a construction machine to which the present invention is applied; and

FIG. 9 is a schematic sectional view showing an engine room according toa conventional technique and devices disposed therein.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

In accordance with the description of the background art, embodiments tobe described below are applied to a digger serving as an example of theconstruction machine according to the present invention.

(First Embodiment)

First, a first embodiment of the present invention will be describedwith reference to FIGS. 1 to 5.

In the first embodiment, following points (i) to (v) are identical tothe background art and conventional technique illustrated in FIGS. 8 and9.

-   (i) An engine room 37 (see FIG. 4) housing an engine 36 is provided    in a rear portion of an upper frame 33.-   (ii) The engine room 37 is a space that is long in a left-right    direction and formed by being surrounded by a base plate 38 of the    upper frame 33, an engine guard member 39 such as a panel material,    a counterweight (not shown) attached to a rear end portion of the    upper frame 33, and so on. The base plate 38 of the upper frame 33    corresponds to a floor forming a bottom surface of the engine room    37. The engine 36 is disposed in the engine room 37 via a mounting    member, not shown in the drawing, so as to extend in the left-right    direction.-   (iii) A left-right pair of vertical plates 40, 41 doubling as    reinforcing members and attachment mounting members are provided in    an intermediate portion of the base plate 38 of the upper frame 33    in a vehicle width direction of the lower propelling body 1. The    vertical plates 40, 41 are provided at an interval in the left-right    direction so as to extend perpendicularly to the base plate 38 along    substantially an entire length of the base plate 38 in a front-rear    direction. The engine 36 is disposed above the vertical plates 40,    41. As a result, a ventilation gap S (see FIG. 4) through which air    can pass is formed in the engine room 37 below the engine 36. More    specifically, the ventilation gap S is formed between the engine 36    and the base plate 38 of the upper frame 33.-   (iv) A hydraulic pump 44 is provided in the engine room 37 on one    side of the engine 36, or more specifically a left side of the    engine 36, while a fan 42 and a heat exchanger 43 such as a radiator    or an oil cooler are provided on an opposite side of the engine 36    to the hydraulic pump 44, or in other words a right side of the    engine 36. An intake port 45 is provided in the vicinity of a right    end of an upper surface wall of the engine guard member 39 covering    the engine room 37. When the fan 42 is rotated, outside air is taken    into the engine room 37 through the intake port 45, and the intake    air forms a cooling airflow that flows through the engine room 37    from the right side to the left side. The airflow includes a lower    airflow that passes through the ventilation gap S, and the heat    exchanger 43 and engine 36 are cooled by this airflow.-   (v) A fire wall 47 is provided in the engine room 37 on the left    side, or in other words the hydraulic pump 44 side. The fire wall 47    is provided to partition the engine 36 from the hydraulic pump 44.    The fire wall 47 is provided to prevent mist-form oil that is leaked    or scattered from the hydraulic pump 44 from falling onto the engine    36, or more accurately an exhaust system of the engine 36 including    a muffler 46.

Note that in FIGS. 1 to 3 and FIG. 6, which shows a second embodiment tobe described below, W denotes a partition plate provided on the baseplate 38 of the upper frame 33 in front of the engine room 37 so as toextend in the left-right direction.

In the first embodiment, with the configurations described above asprerequisites, an air discharge port 48 (see FIGS. 1 and 4) thatcommunicates with the ventilation gap S is formed between the fire wall47 and an upper end of the exhaust side vertical plate 40 positioned onthe left side, and a discharge port 49 is provided in the floor on adownstream side of the lower airflow relative to the exhaust sidevertical plate 40 positioned on the exhaust side of the engine room 37,or in other words the left side. In other words, the discharge port 49is provided in a part of the base plate 38 of the upper frame 33 whichis positioned on the left side of the exhaust side vertical plate 40.

An exhaust duct 50 is provided on the discharge port 49. The lowerairflow passing through the air discharge port 48 is discharged downwardto the outside from the discharge port 49 through the exhaust duct 50.

More specifically, an air inlet 51 for introducing air into the exhaustduct 50 is provided in an upper end of the exhaust duct 50, and adownwardly oriented air outlet 52 that communicates with the dischargeport 49 is provided in a lower end of the exhaust duct 50. A part of theexhaust duct 50 between the upper end air inlet 51 and the lower end airoutlet 52 forms an air passage 53. The air duct 50 is formed as anindependent hollow body and provided such that the air introduced intothe air passage 53 through the air inlet 51 is discharged below theengine room 37 from the air outlet 52 through the discharge port 49.

Incidentally, an outer periphery of a rear end portion of the base plate38 of the upper frame 33, including the part that forms the bottomsurface of the engine room 37, is typically formed in a substantiallyarc-shaped form, as shown in FIGS. 1 and 2, in order to minimize aslewing radius of the upper slewing body 2.

Accordingly, a rear end of the engine room 37 likewise takes asubstantially arc-shaped form that extends along the outer periphery ofthe rear end portion of the upper frame 33.

In the first embodiment, as shown in FIGS. 1 to 4, the base plate 38 ofthe upper frame 33 is composed of a main base plate 54 a and a duct baseplate 54 b. The main base plate 54 a consists mostly of the base plate38. A specific part of the main base plate 54 a which corresponds to aleft rear end portion of the base plate 38 is cut away. Specifically,the cutaway part of the main base plate 54 a is located in a specificregion of the base plate 38, the specific region being located on therear side of the partition plate W and the left side of the exhaust sidevertical plate 40. The duct base plate 54 b is attached to the main baseplate 54 a so as to cover the cutaway part. The discharge port 49 isprovided in an area of the duct base plate 54 b which is located on theinside of the cutaway part. The exhaust duct 50 is mounted on the ductbase plate 54 b such that the exhaust duct 50 is located on the insideof the outer periphery of the left rear end portion of the upper frame33. More specifically, the duct base plate 54 b has an outer edge whichextends along the outer periphery of the left rear end portion of theupper frame 33, and the outer edge is formed in a shape symmetrical to ashape of an outer edge of the right rear end portion of the main baseplate 54 a (the base plate 38). The exhaust duct 50 is located on theinside of the outer edge of the duct base plate 54 b.

In this case, the exhaust duct 50 is provided so as to shield thehydraulic pump 44 from the discharge port 49. More specifically, thehydraulic pump 44 is not directly visible from the outside of the engineroom 37 through the discharge port 49. In other words, the shape, size,and disposal position of the exhaust duct 50 are set such that thehydraulic pump 44 is shielded in this manner.

Further, the exhaust duct 50 has following features (a) and (b).

-   (a) With the aim of improving an effect of preventing leakage of    pump noise, which is noise generated by the hydraulic pump 44, the    exhaust duct 50 is formed in a bent shape including a single bent    portion, as shown in the drawings, thereby substantially taking the    form of a <symbol when seen from a back surface.-   (b) The exhaust duct 50 is disposed below the fire wall 47 such that    the air inlet 51 of the exhaust duct 50 and a lower edge of the air    discharge port 48 are disposed in substantially identical height    positions.

Note that typically, as shown by a dot-dot-dash line drawn inside theexhaust duct 50 in FIG. 4, a sound absorbing material 55 such as glasswool is adhered to an entire inner surface of the exhaust duct 50.

As described above, the exhaust duct 50 formed of a hollow body isprovided on the exhaust side of the engine room 37 so as to shield thehydraulic pump 44 from the discharge port 49. Therefore, pump noiseleakage from the discharge port 49 can be suppressed while dischargingthe lower airflow efficiently to the exterior of the engine room 37through the exhaust duct 50.

Further, in a case where a sound absorbing material is provided toreduce noise, noise can be reduced simply by providing the soundabsorbing material 55 in a concentrated fashion within a limited regionsuch as the inner surface of the exhaust duct 50, and therefore asuperior sound absorbing effect can be secured using the sound absorbingmaterial 55 in a small amount. Moreover, in this case, an amount ofspace on the exhaust side occupied by the sound absorbing material 55can be suppressed, and therefore size and position limitations onexhaust side devices can be relaxed, thereby facilitating installment ofthe devices.

Furthermore, according to this embodiment, following effects (I) to (V)can be obtained.

-   (I) The exhaust duct 50 (the air passage 53) is formed in a bent    shape including a single bent portion, and therefore pump noise    leakage can be suppressed even further by a sound reflection/damping    effect generated inside the exhaust duct 50.-   (II) To ensure that the entire hydraulic pump 44 is not directly    visible from the exterior of the engine room 37 through the    discharge port 49, the exhaust duct 50 is disposed such that the    hydraulic pump 44 is completely shielded from the discharge port 49    by the exhaust duct 50. Therefore, “direct sound” from the hydraulic    pump 44 that leaks directly to the outside through the exhaust duct    50 and the discharge port 49 can be prevented reliably. As a result,    the noise reduction effect can be further improved.-   (III) The exhaust duct 50 is disposed below the fire wall 47, and    therefore the fire wall 47 can be prevented from applying resistance    to the lower airflow. Hence, an exhaust performance, or in other    words a performance relating to an amount of discharged air, can be    improved.-   (IV) The exhaust duct 50 is disposed on the downstream side of the    lower airflow relative to the exhaust side vertical plate 40, and    the fire wall 47 is provided such that the air discharge port 48    communicating with the ventilation gap S is formed between the fire    wall 47 and the upper end of the exhaust side vertical plate 40.    Hence, in a machine such as the digger cited in this embodiment, in    which the vertical plates 40, 41 exist separately on the left and    right sides of the engine room 37, the exhaust side vertical plate    40 does not obstruct the lower airflow, and as a result, a favorable    airflow can be secured.-   (V) A lower edge of the air inlet 51 of the exhaust duct 50 and the    lower edge of the air discharge port 48 are disposed in    substantially identical height positions, and therefore the lower    airflow that passes through the air discharge port 48 from the    ventilation gap S is introduced into the exhaust duct 50 as a    substantially horizontal flow. Hence, little ventilation resistance    is generated on a path along which the air is introduced into the    exhaust duct 50 from the ventilation gap S, and as a result, the air    discharge performance can be improved.

(Second Embodiment)

Next, a second embodiment of the present invention will be describedwith reference to FIG. 6.

Note that only parts of the second embodiment and a following thirdembodiment that differ from the first embodiment will be described.

In the first embodiment, the exhaust duct 50 is mounted on the duct baseplate 54 b such that the exhaust duct 50 is located at a position whichis separated slightly inward from the outer periphery of the left rearend portion of the upper frame 33. In the second embodiment, on theother hand, the exhaust duct 50 is provided on an inner side of theouter periphery of the engine room 37 so as to extend along thesubstantially arc-shaped outer periphery of the engine room 37 disposedin the rear end portion of the upper frame 33.

According to this configuration, the outer peripheral shape of theengine room 37 does not have to be modified in order to dispose theexhaust duct 50, and therefore large design modifications andimprovements to the engine room 37 are not required.

(Third Embodiment)

Next, a third embodiment of the present invention will be described withreference to FIG. 7.

In the third embodiment, the exhaust duct 50 includes an upper sideportion 50 a that extends horizontally in the left-right direction, alower side portion 50 b disposed below and parallel to the upper sideportion 50 a via an interval, and a vertical side portion 50 c disposedperpendicularly to the upper side portion 50 a and the lower sideportion 50 b so as to connect left end portions on identical sides ofthe upper side portion 50 a and the lower side portion 50 b to eachother. Hence, the exhaust duct 50 is formed in the approximate shape ofa U tipped onto its side when seen from a back surface. Further, theexhaust duct 50 is disposed such that the hydraulic pump 44 issandwiched between the upper side portion 50 a and the lower sideportion 50 b.

Note that the air inlet 51 of the exhaust duct 50 is formed over anupper wall, a right side wall and a lower wall on the engine 36 side,which constitute the upper side portion 50 a. The air outlet 52 isformed in a lower wall of the lower side portion 50 b.

According to the third embodiment, the exhaust duct 50 can be disposedwithout modifying the size and position of the hydraulic pump 44.

Further, as described above, the air inlet 51 can be formed to have alarge opening area extending over a wide range of the upper side portion50 a, and therefore the amount of air taken into the exhaust duct 50 canbe increased.

Furthermore, a length of the air passage 53 between the air inlet 51 andthe air outlet 52 can be increased, and therefore the effect of reducingnoise from the pump can be improved.

(Other Embodiments)

-   (1) The exhaust duct 50 may be formed in a bent shape including two    or more bent portions.-   (2) To ensure that the entire hydraulic pump 44 is not directly    visible from the exterior of the engine room 37 through the    discharge port 49, the exhaust duct 50 is preferably disposed such    that the hydraulic pump 44 is completely shielded from the discharge    port 49 by the exhaust duct 50, as in the above embodiments. In    practical terms, however, as long as a required shielding effect in    relation to the hydraulic pump 44, or in other words a required pump    noise reduction effect, can be secured, the exhaust duct may be    disposed to shield the hydraulic pump 44 from the outside while    permitting a part of the hydraulic pump 44 to be directly visible    from the outside.-   (3) In the above embodiments, the exhaust duct 50 is formed as an    independent hollow body, but a structure of the upper slewing body,    such as the partition plate W, the engine guard member 39, or the    counterweight, may be used as a part of the exhaust duct.-   (4) The present invention is not limited to a digger, and may be    applied widely to a construction machine in which an engine is    disposed in an engine room formed in a rear portion of an upper    frame, a fan is disposed on one side of the engine, a hydraulic pump    is disposed on an opposite side of the engine to the fan, and a    lower airflow that passes through a ventilation gap below the engine    is generated. For example, the present invention may be applied to a    demolition machine, a crusher, or the like formed using a digger as    a base.

[Summary of the Embodiments]

The embodiments described above may be summarized as follows.

A construction machine according to the embodiments includes: an engineroom; a floor constituting a bottom surface of the engine room; anengine provided in the engine room such that a ventilation gap is formedbelow the engine; a hydraulic pump provided in the engine room on anexhaust side serving as one side of the engine; a fan which is providedin the engine room on an intake side serving as an opposite side of theengine to the hydraulic pump, and which, when the fan is rotated,generates a cooling airflow that includes a lower airflow passingthrough the ventilation gap and flows from the intake side to theexhaust side; and an exhaust duct formed of a hollow body to dischargethe lower airflow to an exterior of the engine room, wherein a dischargeport is provided in a part of the floor on the exhaust side, an airinlet for introducing air into the exhaust duct is provided in an upperportion of the exhaust duct, an air outlet for discharging the air fromthe exhaust duct is provided in a lower portion of the exhaust duct, anair passage is formed in an interior of the exhaust duct between the airinlet and the air outlet, and the exhaust duct is disposed on theexhaust side of the engine room such that the air introduced into theair passage in the exhaust duct through the air inlet is dischargedbelow the engine room from the air outlet through the discharge port andthe hydraulic pump is shielded from the discharge port by the exhaustduct.

In this configuration, the exhaust duct formed of a hollow body isprovided on the exhaust side of the engine room so as to shield thehydraulic pump from the discharge port connected to the outside.Therefore, pump noise leakage through the discharge port can besuppressed while discharging the lower airflow efficiently to theexterior of the engine room through the exhaust duct. Further, with thisconfiguration, when a sound absorbing material is provided, pump noisecan be absorbed effectively simply by providing the sound absorbingmaterial in a concentrated fashion within a limited region such as aninner surface of the exhaust duct, and therefore a superior soundabsorption effect can be secured with a small amount of the soundabsorbing material. Moreover, size and position limitations on devicesprovided on the exhaust side can be relaxed, thereby facilitatinginstallment of the devices.

In the construction machine described above, the air passage in theexhaust duct is preferably formed in a bent shape including at least onebent portion.

According to this configuration, a sound reflection/damping effectgenerated inside the exhaust duct is enhanced by the bent shape of theexhaust duct, and therefore pump noise leakage can be suppressed evenfurther.

In the construction machine described above, the exhaust duct ispreferably disposed to shield the hydraulic pump from the discharge portso that the hydraulic pump is not directly visible from the outsidethrough the discharge port.

According to this configuration, “direct sound” can be preventedcompletely, enabling a further improvement in the noise reductioneffect.

In the construction machine described above, a fire wall, whichpartitions the engine from the hydraulic pump, is preferably provided onthe exhaust side of the engine room, and the exhaust duct is preferablydisposed below the fire wall.

According to this configuration, the fire wall does not apply resistanceto the lower airflow, and therefore the exhaust performance, or in otherwords the performance relating to the amount of discharged air, can beimproved.

Preferably in this case, the construction machine further comprises alower propelling body and an upper slewing body carried on the lowerpropelling body, the upper slewing body includes an upper frame, aleft-right pair of vertical plates extending in a front-rear directionarc provided in a central portion of the upper frame in a vehicle widthdirection of the lower propelling body, the engine room is formed in arear portion of the upper frame, the engine is disposed in the engineroom so as to extend in a left-right direction, and the exhaust duct isdisposed on a downstream side of the lower airflow relative to aspecific vertical plate of the left-right pair of vertical plates, thespecific vertical plate disposed on the exhaust side, while the firewall is provided such that an air discharge port which communicates withthe ventilation gap is formed between the fire wall and an upper end ofthe vertical plate disposed on the exhaust side.

According to this configuration, in a machine such as a digger, in whichthe vertical plates exist on the left and right sides of the engineroom, the exhaust side vertical plate does not obstruct the lowerairflow, and as a result, a favorable airflow can be secured.

Also in this case, a lower edge of the air inlet in the exhaust duct anda lower edge of the air discharge port are preferably disposed insubstantially identical height positions.

According to this configuration, the lower airflow that passes throughthe air discharge port from the ventilation gap is introduced into theexhaust duct as a substantially horizontal flow, enabling a reduction inventilation resistance generated on a path along which the airflow isintroduced into the exhaust duct from the ventilation gap. As a result,the air discharge performance can be improved.

In the construction machine described above, the exhaust duct preferablyhas an upper side portion, a lower side portion disposed below andparallel to the upper side portion via an interval, and a vertical sideportion disposed perpendicularly to the upper side portion and the lowerside portion so as to connect end portions on identical sides of theupper side portion and the lower side portion to each other, the exhaustduct disposed such that the hydraulic pump is sandwiched between theupper side portion and the lower side portion.

According to this configuration, the exhaust duct can be disposedwithout modifying the size and position of the hydraulic pump. Further,with this configuration, the air inlet can be formed to have a largeopening area extending over a wide range of the upper side portionpositioned in the upper portion of the exhaust duct, and therefore theamount of air taken into the exhaust duct can be increased. Furthermore,with this configuration, great length can be secured in the air passagebetween the air inlet and the air outlet, and therefore the pump noisereduction effect of the exhaust duct can be improved.

In the construction machine described above, the exhaust duct ispreferably provided on an inner side of an outer periphery of the engineroom so as to extend along the outer periphery of the engine room.

According to this configuration, the outer peripheral shape of theengine room does not have to be modified in order to dispose the exhaustduct, and therefore large design modifications and improvements to theengine room are not required.

According to the embodiments described above, pump noise leakage from aconstruction machine can be suppressed while improving an air dischargeperformance of a lower airflow flowing under an engine, and when a soundabsorbing material is provided, device installation can be facilitatedwhile securing a superior sound absorption effect with a small amount ofthe sound absorbing material.

This application is based on Japanese Patent application No. 2011-218938filed in Japan Patent Office on Oct. 3, 2011, the contents of which arehereby incorporated by reference.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention hereinafterdefined, they should be construed as being included therein.

What is claimed is:
 1. A construction machine, comprising: an engineroom; a floor constituting a bottom surface of the engine room; anengine provided in the engine room such that a ventilation gap is formedbelow the engine; a hydraulic pump provided in the engine room on anexhaust side serving as one side of the engine; a fan which is providedin the engine room on an intake side serving as an opposite side of theengine to the hydraulic pump, and which, when the fan is rotated,generates a cooling airflow that includes a lower airflow passingthrough the ventilation gap and flows from the intake side to theexhaust side; a vertical plate member standing up on the floor, thevertical plate member having an upper plate end located just below thehydraulic pump, the upper plate end allowing the airflow having passedthrough the ventilation gap to pass over the upper plate end to theexhaust side; and an exhaust duct formed of a hollow body to dischargethe lower airflow to an exterior of the engine room, wherein a dischargeport is provided in a part of the floor on the exhaust side of thevertical plate member, the exhaust duct has a duct wall standing up onthe floor around the discharge port and surrounding an air passageextending vertically above the discharge port, the air passage openedupward to form an air inlet and opened downward to form an air outlet,the duct wall having an upper portion and a lower end, the upper portionsurrounding the air inlet at a position higher than the upper surface ofthe floor to allow the airflow having passed over the upper plate end tobe introduced into the air passage through the air inlet at the positionhigher than the upper surface of the floor, the position allowing theduct wall under the air inlet to be interposed between the hydraulicpump and the discharge port so as to shield the discharge port from thehydraulic pump, the lower end forming the air outlet for discharging theair from the exhaust duct, and the air passage is formed in an interiorof the exhaust duct between the air inlet and the air outlet, and thelower end of the duct wall is mounted on the floor to surround thedischarge port and disposed on the exhaust side of the engine room suchthat the air introduced into the air passage in the exhaust duct throughthe air inlet is discharged below the engine room from the air outletthrough the discharge port and the hydraulic pump is shielded from thedischarge port by the exhaust duct.
 2. The construction machineaccording to claim 1, wherein a fire wall, which partitions the enginefrom the hydraulic pump, is provided on the exhaust side of the engineroom, and the exhaust duct is disposed below the fire wall.
 3. Theconstruction machine according to claim 2, further comprising a lowerpropelling body and an upper slewing body carried on the lowerpropelling body, wherein the upper slewing body includes an upper frame,a left-right pair of vertical plates including the vertical plate memberare provided in a central portion of the upper frame in a vehicle widthdirection of the lower propelling body, each of the vertical platesextending in a front-rear direction, the engine room is formed in a rearportion of the upper frame, the engine is disposed in the engine room soas to extend in a left-right direction, and the exhaust duct is disposedon a downstream side of the lower airflow relative to a specificvertical plate of the left-right pair of vertical plates, the specificvertical plate disposed on the exhaust side, while the fire wall isprovided such that an air discharge port which communicates with theventilation gap is formed between the fire wall and an upper end of thevertical plate disposed on the exhaust side.
 4. The construction machineaccording to claim 3, wherein a lower edge of the air inlet in theexhaust duct and a lower edge of the air discharge port are disposed insubstantially identical height positions.
 5. The construction machineaccording to claim 1, wherein the air passage in the exhaust duct isformed in a bent shape including at least one bent portion.
 6. Theconstruction machine according to claim 1, wherein the exhaust duct isdisposed to shield the hydraulic pump from the discharge port so thatthe hydraulic pump is not directly visible from the outside through thedischarge port.
 7. The construction machine according to claim 1,wherein the exhaust duct has an upper side portion, a lower side portiondisposed below and parallel to the upper side portion via an interval,and a vertical side portion disposed perpendicularly to the upper sideportion and the lower side portion so as to connect end portions onidentical sides of the upper side portion and the lower side portion toeach other, the exhaust duct disposed such that the hydraulic pump issandwiched between the upper side portion and the lower side portion. 8.The construction machine according to claim 1, wherein the exhaust ductis provided on an inner side of an outer periphery of the engine room soas to extend along the outer periphery of the engine room.